San Francisco Giants' Marco Scutaro celebrates after Game 7 of baseball's National League championship series against the St. Louis Cardinals Monday, Oct. 22, 2012, in San Francisco. The Giants won 9-0 to win the series. Scutaro was named the series MVP.

Photo: David J. Phillip, Associated Press

San Francisco Giants' Marco Scutaro celebrates after Game 7 of...

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Marco Scutaro pointed to the crowd with a big grin as he made his way down Market Street. The San Francisco Giants celebrated their second World Series title in three years with a parade down Market Street Wednesday October 31, 2012.

Photo: Brant Ward, The Chronicle

Marco Scutaro pointed to the crowd with a big grin as he made his...

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Marco Scutaro and Brandon Belt celebrate the Giants' World Series win after game 4 of the World Series at Comerica Park on Sunday, Oct. 28, 2012 in Detroit, MI.

Photo: Michael Macor, The Chronicle

Marco Scutaro and Brandon Belt celebrate the Giants' World Series...

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Giants' 2nd baseman Marco Scutaro scoops up a Tigers' left fielder Quintin Berry grounder in the 1st inning during game 4 of the World Series at Comerica Park on Sunday, Oct. 28, 2012 in Detroit, MI.

Photo: Lance Iversen, The Chronicle

Giants' 2nd baseman Marco Scutaro scoops up a Tigers' left fielder...

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Marco Scutaro singles in a run in the seventh inning during the World Series game 1 at AT&T Park in San Francisco, Calif., on Wednesday, Oct. 24, 2012.

Photo: Brant Ward, The Chronicle

Marco Scutaro singles in a run in the seventh inning during the...

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Marco Scutaro was the Giants' number one preference to play second base after hitting .362 following his July acquisition.

Photo: Carlos Avila Gonzalez, The Chronicle

Marco Scutaro was the Giants' number one preference to play second...

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Giants' DH Ryan Theriot reacts as he crosses the plate in the 10th inning on a Marco Scutaro single during game 4 of the World Series at Comerica Park on Sunday, Oct. 28, 2012 in Detroit, MI.

The Giants went 3-for-3 with their key free agents, and it cost them $78 million.

The price of being champions.

Second baseman Marco Scutaro joined the mix late Tuesday, agreeing to a three-year, $20-million contract that'll keep him a Giant through 2015. On Oct. 30 of that year, he turns 40.

"If he can survive (Matt) Holliday at second base, it gives me a lot of confidence he can survive into his late 30s," said assistant GM Bobby Evans in a light-hearted reference to the memorable NLCS collision.

Scutaro hit .362 after arriving in a July 27 trade with Colorado and was MVP of the NLCS.

The Scutaro deal came one day after center fielder Angel Pagan agreed to a four-year, $40 million contract. Reliever Jeremy Affeldt already had a three-year, $18 million deal.

"They were our priority," Evans said. "We had the benefit that all three wanted to come back. We have a very special group, and they all showed loyalty in coming back to us and the fans. They could've stayed out there and tried to get bigger deals. It's a tribute to them."

Just like that, the Giants' roster nucleus is virtually set, give or take a platoon left fielder and right-handed reliever. They've got all the key parts in place from the team that won a second championship in three years.

Tuesday afternoon, the Giants had a two-year offer with a vesting option on the table for Scutaro. The belief was that another team had a two-year deal with a higher average annual value, but Scutaro's camp preferred a third year, even at a lesser average value. Once the Giants guaranteed a third year, Scutaro jumped at it.